1. Field of the Invention
This invention relates to a novel resinous substance which can be used for a wide variety of applications including the preparation of electronic materials such as insulators and sealing agents, optical materials, casting materials, lamination materials, pressure sensitive adhesives, adhesives, paints, inks, and modifiers for resins.
2. Description of the Prior Art
Rosin compounds are used in inks, paints, adhesives pressure sensitive adhesives, etc. consisting mainly of rubber or acrylic resins as additives for improving their adhesion to the substrate. They are also used in paper sizes, as they have high water-repelling property. Moreover, they are used for preparing insulating materials, as they exhibit high electrical insulating property.
Natural pine rosin is a mixture of abietic acid and other compounds having backbones which are similar to that of abietic acid, and is used as the principal material for various rosin compounds. It is, however, known that a number of problems arise from the use of natural pine rosin. For example, the compounds composing natural pine rosin, such as abietic acid, generally have the diene structure and are likely to have their properties affected easily by oxygen, heat, light, etc.
Stabilized rosins which are obtained by reacting the diene structure of natural pine rosin and stabilizing it are, therefore, widely used. The known stabilized rosins include maleic rosin obtained by adding maleic anhydride to the diene structure, rosin obtained by adding fumaric acid, phenolically modified rosin obtained by adding a phenolic resin, polymerized (or dimerized) rosin obtained by dimerizing the diene structure, disproportionated rosin obtained by disproportionating the rosin-components, such as abietic acid, to form monoenes and aromatic rings, and hydrogenated rosin obtained by hydrogenating the diene structure.
Natural pine rosin has so low a softening point that, when it is used in an adhesive, pressure sensitive adhesives, etc. consisting mainly of a rubber or acrylic resin, it greatly lowers the cohesive force and heat resistance of the adhesive, etc., though it improves its adhesive property. Therefore, a rosin compound having a higher softening point has been made by esterifying natural pine rosin using a polyhydric alcohol, such as ethylene glycol, glycerin, or pentaerithritol.
The esterified products of natural pine rosin, however, still retain the diene structure and are, therefore likely to have their properties affected by oxygen, heat, light, etc. Accordingly, it is often the case to use, as well as the esters of natural pine rosin, rosin compounds obtained by esterifying stabilized rosins, such as maleic polymerized (dimerized), disproportionated, or hydrogenated rosins.
The esterified rosin compounds having high softening points are, however, still unsatisfactory when used for modifying acrylic or rubber resins. They lower the cohesive force of the resin, though not so much as natural pine rosin or stabilized rosins do.
The rosin compounds have adhesive, water-repelling, and other properties, and are used in inks, paints, adhesives or pressure sensitive adhesives consisting mainly of rubber or acrylic resins, in sizes, etc, as hereinabove stated. However, there has hardly been any case where the rosin compounds are used in sealing, optical, casting, lamination, or other materials composed of epoxy or methacrylic resins. This is probably due to the unsatisfactory compatibility of the rosin compounds with the epoxy and methacrylic resins.